The cross-linking agent N^V'-methylenebisacrylamide (MBA, Acros), redox couple potassium persulphate (KPS, Merck, p.a.) and potassium pyrosulphate
(KPyS, Merck p.a.), were applied without further purification.
Potassium persulphate (PPS) and potassium pyrosulphate
(PPyroS), the initiator and accelerator, were obtained from Merck & Co.
The reaction was then rinsed in 4,5% sodium pyrosulphate
for 50 seconds.
The active anticalculus ingredients in the test group were tetrapotassium pyrophosphate, PEG-6, disodium pyrophosphate, and tetrasodium pyrosulphate
comprising a 5.0% soluble pyrophosphate formulation (Proctor and Gamble, Cincinnati, Ohio).